Many telephone subscribers, particularly large business entities, provide sophisticated and diverse services and information to their customers over the telephone. A particular calling party who is a customer of the subscriber may initially reach the subscriber by dialing a toll free or "800" type number provided by the subscriber. The calling party may then be connected to a "primary" subscriber location that is designated to answer calls placed to the subscriber from customers who originate calls from certain origination areas, e.g., originating area codes or telephone exchanges. It may then be determined that the attendant or other personnel at the primary subscriber location cannot fully service the customer. In that event, the attendant at the primary subscriber location may desire to reroute or redirect the call to an "alternate" location that is better equipped to handle or complete the call. This alternate location may be reached by dialing another 800 number, which may be provided by the same subscriber or by another 800 subscriber.
If the primary subscriber location is served by a private branch exchange (PBX), the transfer of an incoming call arriving via a first trunk, to an alternate subscriber location not served by the PBX, is presently accommodated by placing a second call to the alternate location using another, outgoing, trunk, and then bridging the incoming and outgoing calls. This type of call transfer arrangement incurs additional billed cost for the subscriber, since the subscriber continues to be billed for the call because the call continues to be routed through the PBX at the primary subscriber location. This charge may not benefit the subscriber, because the attendant at the primary location may no longer be "on the call" or talking. Also, the communications service provided to the calling party while the call continues to be routed through the PBX at the primary subscriber location can be sub-optimum, due to the "hair-pinning" of two subscriber grade trunks through the PBX to complete the transfer, effectively reducting the capacity of the PBX to handle other calls. In addition, the second call is treated as though it originated from the primary subscriber location, creating certain other routing problems described below.
If the call is placed through a network based adjunct processor, such as the Modular Services Node (MSN) described in U.S. Pat. No. 4,878,240 issued to S. M. Lin et al. on Oct. 31, 1989, the PBX hair-pinning problem can be avoided, since the MSN is located in the telephone network. However, in the Lin arrangement, the transferred call is not treated as originating from the calling party at the customer location. This is particularly troublesome in the case of "intelligent" call processing, in which the specific call treatment (routing) given to an 800 type call depends, among other factors, on where the call originated. Specifically, since the transferred call resembles a new call made in the adjunct, as opposed to originating at the customer location, the call may be routed to an alternate location that is different from the location to which the subscriber of the 800 number would wish to route calls from customers at that location. Intelligent call processing is normally associated with toll-free (800 number) calling, but will, in the future, also be available with respect to other telephone services.
Call redirection or rerouting also raises issues with respect to call billing. In particular, at the present time, when a call from a customer location to a primary location is subsequently redirected or rerouted to an alternate location, the party paying for the original call (the subscriber in the case of 800 type calls) will be charged for the cost of the entire time period of both the original and redirected calls, even though the attendant or personnel at the primary subscriber location may not participate in the call after redirection or rerouting to the alternate location. If the same subscriber provided the 800 number for the alternate location, which is typical, the same subscriber will also pay the cost of the redirected call for the time period of the redirected call. This subscriber may then, is essence, be charged twice for a portion of the time period of the redirected call, leading to subscriber dissatisfaction.
In the realm of 800 and other intelligent call processing services, one can easily see that a call redirection feature is needed that allows a call made to a primary location that is answered and determined to be better served by personnel at another location, to be rerouted to an alternate location, and yet to retain the original caller's identity, so that the appropriate routing or feature logic is invoked. This rerouting should be accomplished without utilizing superfluous network and PBX resources, without adding unnecessary subscriber loops to the talk path, and without charging the 800 subscriber for any portion of the redirected call which the subscriber is not actually "using".